1. The Field Of The Invention
The present invention relates to a rotary cam low insertion force connector assembly which includes a low insertion force connector, a daughter board header, and a combination cam actuating rod and card guide member, the latter two being attached to the equipment frame adjacent one end of the connector.
2. The Prior Art
The low insertion force connector portion of the present assembly is described in detail in U.S. Pat. No. 3,899,234 issued Aug. 12, 1975. The present assembly is designed to incorporate the above-mentioned low insertion force connector in a two-part embodiment with an improved actuating means for remotely actuating the cam member of the connector.
An essential requirement to assure reliable operation of printed wiring boards under all environmental conditions, such as those encountered in military service, is that the boards must be thoroughly cleaned and protected with a thin conformal coating as a last step in production. Contamination can be introduced on the printed wiring board surfaces through handling, storage and exposure during operation. These contaminants may be metal particles or other conductive and ionizable materials. Also, they may be organic materials which will support fungus. The presence of these materials on the surface of the board degrades the insulation resistance, and, in the case of conductive contaminants, can result in excessive electrical leakage or shorts between conductors in the presence of moisture. The protection of the clean surface of the board by the protective coating precludes this degradation from occurring since the conductors are enveloped in the coating and contaminants can only attach themselves to the insulating surface of the coating.
Since the contact pads on the printed circuit board that mate with a one-part printed circuit receptacle cannot be comformally coated, the use of this type of connector seriously compromises the reliability of a printed circuit assembly under some environmental circumstances. Further, the one-part connector receptacle may constitute a moisture trap which could aggravate the condition.
In the past, equipment using one-part connectors has been maintained by burnishing the printed contacts and the receptacle contacts with an abrasive (No. 0000 sandpaper) to remove corrosion. When the situation became sufficiently aggravated by corrosion to preclude burnishing the contacts, the subassemblies were replaced. Since the connector portion of the printed wiring subassembly is an integral part of the conductor pattern, no corrective action is possible and the entire assembly must be scrapped. The cost of subassemblies vary considerably; however, an estimated average minimum cost of several hundred dollars is not unreasonable. Considering this, the scrapping of a subassembly because the connector cannot be replaced is intolerable.
A frequently expressed argument offered for justifying the use of the one-part connector is that of lower cost. The cost of a two-part connector should be compared to the cost of a one-part receptacle after including the additional costs imposed on the latter because of the special processing required for the plating of the printed wiring board contact tabs and for the machining of the board to assure proper initial entry and alignment of the board into the receptacle. Additional costs would also be involved to achieve more stringent dimensional and stability control of the printed wiring board base material for satisfactory life characteristics. If all these costs are considered, the differential is insignificant and, in some instances, even favors the two-part connector.
It is also desirable to have a rotary cam low insertion force connector which can be remotely operated. This is especially true for instances of high density installations with many closely spaced printed circuit boards. In such cases it is preferable to have actuating means convenient to the side of the printed circuit board remote from the connector, which means control the cam of the connector.